Under so-called revolving-door laws to prevent conflicts of interest, Cabinet members who leave the government are subject to a two-year ban on lobbying at their former agency, but they may lobby Congress immediately, according to a Congressional Research Service report in 2012.

The two-year ban also prevents them from lobbying top officials at any federal executive-branch department or agency, the report said.

LaHood heads to DLA Piper with his former chief of staff at Transportation, Joan DeBoer, who will become a policy adviser, the law firm said. Earlier she worked in Congress for LaHood and his predecessor, former Rep. Bob Michel, R-Ill.

DLA Piper has more than 4,200 lawyers in more than 30 countries in the Americas, Asia, Europe and the Middle East, the firm said.